Based on our preliminary data, we will perform the following paradigms in the second phase: 1) sham 2) dual stimulation 3) optimized tDCS in a randomized counterbalanced order. The optimized tDCS will be determined during a test session prior to the first treatment where the tDCS montage producing the best behavioral response will be used during therapy. Subjects will perform this under IRB approved study # STU 102013-085.